Bite force and its correlations in different denture types

Maximal bite force was measured and intraoral condition was examined in 89 patients at the Institute of Dentistry, University of Turku. These patients formed three different denture groups: those with complete dentures, those with full maxillary denture and partial mandibular denture, and those with natural dentition or skeleton-supported partial maxillary denture and partial mandibular denture. There were three age groups: greater than or equal to 70, 60-69, and less than or equal to 59 years old. Maximal bite force was recorded with an appliance at seven different measuring points by placing a biting fork between the antagonistic teeth while at the same time the occlusion was stabilized contralaterally with a plastic tube. Maximal bite force had a correlation with age and sex (P less than 0.01). In partial-denture groups high bite force had a correlation with the breaking of dentures (P less than 0.001 and P less than 0.05, respectively). Satisfied patients had a higher bite force than dissatisfied ones. When there was some disturbance in occlusion, the bite force was smaller, especially in full-denture groups (P less than 0.001). Full-denture wearers also had a good bite force, but the best biting area was located more posteriorly than in patients who still had some natural teeth left in both jaws. Changes in the denture-bearing mucosa in patients with complete dentures and negative height of the mandibular alveolar process decreased the bite force slightly.     

An implant-supported overdenture in an edentulous upper jaw

An implant-supported overdenture is a good alternative treatment to a conventional denture for patients with complaints about the retention and stability of their removable complete denture. These complaints more often have to do with the mandibular than the maxillary denture. Implant-supported overdentures offer better results in the mandible than in the maxilla. In cases of insujficient bone volume in the maxilla for inserting implants, maxillary sinus floor elevation using an autogenous bone graft from the oral cavity or the iliac crest may be carried out. Treatment of the edentulous maxilla by inserting 6 implants followed by manufacturing a bar-clip mesostructure and an implant-supported overdenture is the most successful, followed closely by the treatment option of inserting 4 implants and fabricating a similar mesostructure and overdenture. Aftercare by routine preventive examinations is required.     

Masticatory function and patient satisfaction with implant-supported mandibular overdentures: a prospective 5-year study

PURPOSE: The aim of this study was to assess the outcome of treatment with implant-supported mandibular overdentures in terms of biting and chewing, in entirely satisfied and not fully satisfied patients. MATERIALS AND METHODS: Twelve edentulous patients who had worn dentures for at least 5 years participated. They were in good health but had retention problems with their mandibular dentures. First, all patients received new dentures. After 3 months, two Astra Tech implants were placed in the anterior part of the mandible, and 6 months later the abutments were connected. Patient assessment (questionnaire) and functional recordings (chewing ability, bite force, electromyographic activity) were performed with the new dentures, and again 3 months, 1 year, and 5 years after overdenture treatment. RESULTS: After treatment, all patients were able to comminute hard and tough food, the maximum bite force and the chewing activity increased in parallel, and the duration of the chewing cycle was reduced. Every patient felt improved function and reduction of chewing pain. However, the seven patients not fully satisfied with the function of the implant-supported mandibular overdentures were characterized by lower muscle activity, even before implant placement, than the entirely satisfied patients. CONCLUSION: Implant-supported mandibular overdenture treatment permits better biting and chewing function than conventional complete dentures.     

Maxillary anterior and mandibular posterior residual ridge resorption in patients wearing a mandibular implant-retained overdenture

The mandibular implant-retained overdenture could improve masticatory function compared to the conventional complete denture. However, increased forces exerted by the overdenture could increase residual ridge resorption of the maxillary anterior and mandibular posterior areas. The aim of this study was to compare the effect of the mandibular implant-retained overdenture using two or four dental implants, or the conventional complete denture on resorption of the residual ridge of the maxillary anterior and mandibular posterior areas over a period of 10 years. In total, 120 patients, 30 patients treated with an overdenture on two implants (two-implant group), 30 patients with an overdenture on four implants (four-implant group) and 60 patients treated with a conventional full denture (conventional group), participated in this study. On panoramic radiographs, made before and 10 years after treatment, proportional area measurements were applied to determine changes in bone height. After 10 years, a statistically significant amount of bone resorption had occurred in the anterior maxilla in the two-implant group and in the four-implant group. A significant amount of bone resorption had occurred in the posterior mandible in all three groups. There were no statistically significant differences between the groups in both areas. Patients presented large individual differences. It is concluded that patients rehabilitated with implant-retained mandibular overdentures are not subjected to more residual ridge resorption in the anterior maxilla when compared to patients wearing a conventional full denture. Regarding the mandibular posterior residual ridge, resorption was irrespective of wearing an implant-retained mandibular overdenture or a conventional mandibular denture.     

In vivo force measurements on maxillary implants supporting a fixed prosthesis or an overdenture: a pilot study

STATEMENT OF PROBLEM: In this preliminary study, an attempt was made to measure in vivo forces simultaneously on 5 maxillary implants with different types of superstructure. MATERIAL AND METHODS: Force measurements were carried out on 1 test patient with 5 ITI implants in the edentulous maxilla. A screw-retained fixed complete denture and an overdenture were fabricated for comparative measurements of forces. The overdenture could be mounted to 2 different types of bars. The measuring method was used with piezo-electric force transducers that were directly mounted onto the implants. This allowed for simultaneous measurements of forces in 3 dimensions, ie, in axial and transverse directions. Static and functional forces such as maximum biting (clenching), biting on a bite plate, and chewing food were registered. All measurements were repeated in the same way 2 years later. RESULTS: The registered forces exhibited similar force patterns with both types of superstructure and both types of bars for overdenture connection. The force magnitudes were significantly different for the 3 dimensions (P<.05) with highest forces along the implant axis. On the posterior implants, force magnitudes were significantly higher (P<.05) than on the anterior implants in all 3 dimensions. On the anterior implants, under some test conditions, the transverse force components reached up to 100% of the axial force or even exceeded it during the chewing of food. During maximum biting, no upward force (tensile force) was found on any implant with the fixed complete denture, but upward force was found on one anterior implant with the overdenture. When chewing food, small force magnitudes in upward directions were regularly found with both superstructures. The force patterns between the first and second registrations showed similar trends, and no obvious differences were found. CONCLUSION: From these results it was concluded that similar patterns of force transmission onto the implants are observed with a fixed complete denture and an overdenture connected to maxillary implants. The bar design did not significantly influence the force pattern.     

The effect of denture stability on bite force and muscular effort

This study tested the hypothesis that denture instability limits the amount of voluntary muscular effort generated by denture wearers. Seventeen edentulous subjects (seven men, 10 women; mean age 60·3 ± 13·0 years) with newly acquired implant-retained mandibular overdentures and a conventional maxillary denture participated. Maximum bite forces and corresponding electromyographic (EMG) activity from the temporalis and masseter muscles (bilaterally) were recorded under two experimental conditions: (i) Unilateral premolar and molar bites without additional support, and (ii) premolar and molar bites with bite block support on the opposite side. In addition, EMG values alone were recorded during maximum clenching without any transducer between the upper and lower dentures. The level of muscular effort was significantly higher with greater denture support. These results indicate that denture instability probably prevents denture wearers from using the full potential of their jaw muscles, especially during unilateral biting and chewing, even with two implants supporting the mandibular dentures.     

The effect of different mandibular dentures on antagonistic maxillary ridge

PURPOSE: Is to evaluate the antagonistic, maxillary ridge resorption for different prosthetic modalities mainly mucosa-supported mandibular complete overdentures, combined mucosa implant-supported mandibular complete overdenture, and lower conventional complete dentures. MATERIALS AND METHODS: Fifteen completely edentulous patients were divided into 3 groups; 5 patients each. Group I patients received maxillary conventional denture and mandibular overdentures retained by magnet attachment on 2 implants (mainly mucosa-supported overdenture). Group II patients received maxillary conventional denture and mandibular overdentures retained by bar attachment on 2 implants (combined mucosa implant-supported overdenture). Group III patients received upper and lower conventional complete denture. All patients were evaluated clinically and radiographically immediately after insertion and after 1 and 2 years. Panoramic radiographic film was used to evaluate the antagonistic maxillary ridge resorption. RESULTS: Indicated a more pronounced annual bone resorption of the antagonistic maxillary ridge after 2 years in patients with conventional complete denture wearers when compared with patients with combined mucosa implant-supported mandibular complete overdenture and mainly mucosa-supported mandibular complete overdenture groups. CONCLUSION: Using a combined mucosa implant-supported mandibular complete overdenture the amount of antagonistic maxillary alveolar bone resorption increases when compared with the mainly mucosa-supported complete overdenture.     

Patient satisfaction and preference with magnet, bar-clip, and ball-socket retained mandibular implant overdentures: a cross-over clinical trial

PURPOSE: The purposes of this study were to: (1) determine patient satisfaction with implant-supported mandibular overdentures using magnet, bar-clip, and ball-socket attachments; and (2) assess the relation between maximum bite force and patient satisfaction. MATERIALS AND METHODS: In a cross-over clinical trial, 18 edentulous patients with mandibular denture complaints received two mandibular implants and new mandibular and maxillary dentures. The mandibular denture was initially without any kind of attachment system, but it was fitted with one of the attachment types after 3 months. The attachments were changed 3 months thereafter, in random order. A questionnaire on denture complaints was administered at baseline (with the old denture), after 3 months of function with the new denture without attachments, and after 3 months of function with each of the attachments (within-subject comparison). In addition, patients were asked to express their overall appreciation of their dentures on a VAS. Patients' preferences were determined at the end of the experiment. Maximum bite forces were obtained from a previous study with the same population. Five scales of denture complaints were constructed. Mean scale and VAS scores at the five evaluation points were compared among the groups. Pearson correlation was calculated between maximum bite force and scale and VAS scores. RESULTS AND CONCLUSION: Mandibular implant-supported overdenture treatment reduced various denture complaints. The VAS score better reflected patients' preferences than did scale score. Patients strongly preferred bar-clip (10/18 subjects) and ball-socket attachments (7/18 subjects) over magnet attachments (1/18 subjects). Patients' preferences could not be predicted on the basis of baseline observations. Maximum bite force was not correlated to scale or VAS score. Hence, patients with higher maximum bite forces were not necessarily more satisfied.     

Masticatory performance with mandibular implant-retained overdentures

It was investigated in a clinical trial whether the masticatory performance of complete-denture wearers depended on the support for their mandibular dentures by implants or mucosa. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture (mucosa-borne), a mandibular overdenture retained by two IMZ-implants (implant-mucosa-borne), or a mandibular overdenture on a transmandibular implant (TMI; mainly implant-borne). In comparison with mandibular implant-retained overdentures, subjects with conventional dentures needed 1.5 to 3.6 times more chewing strokes for an equivalent reduction in particle size. No differences in masticatory performance were found between subjects with IMZ-implants and those with TMI. This suggests that the increased stability of the mandibular denture with implants determines the wearer's masticatory performance, rather than the support by implants.     

Two-center clinical trial of implant–retained mandibular overdentures versus complete dentures – chewing ability

Abstract This study is a two-center clinical trial with the aim to assess the treatment effects of implant-retained mandibular overdentures versus conventional complete dentures. Treatment had been assigned according to a balanced allocation method. The following criteria were used to enhance the comparability of the treatment groups: age, gender, the edentulous period of the mandible, the number of previously made mandibular dentures, the number of years having worn the present mandibular denture and the symphyseal bone height. 151 patients with severely resorbed mandibles participated in the study, they were treated at two centers. Ninety-one patients received an implant-retained mandibular overdenture (IRO) and 60 patients a conventional complete denture (CD). Since some patients refused the allocated treatment the “Intention To Treat” principle was applied. This implies that patients are evaluated in the originally allocated treatment group regardless of the actual treatment they received. Patient's experiences were evaluated before treatment and I yr after insertion of the new dentures. Results before treatment showed that both treatment groups were comparable: they were dissatisfied with their mandibular denture and they could hardly chew tough or hard foods. One year after insertion of the new dentures the IRO-group was satisfied with their mandibular denture, whereas only one third of the CD-group was satisfied. With respect to the chewing ability the IRO-group scored significantly better than the CD-group (P0.0001).     

The influence of resilient liner and clip attachments for bar‐implant‐retained mandibular overdentures on opposing maxillary ridge. A 5‐year randomised clinical trial

This study aimed to compare the influence of resilient liner and clip attachments for bar‐implant‐retained mandibular overdentures on opposing maxillary ridge after 5 years of denture wearing. Thirty edentulous male patients (mean age 62·5 years) received two implants in the anterior mandible after being allocated into two equal groups using balanced randomisation. After 3 months, implants were connected with resilient bars. New maxillary complete dentures were then constructed, and mandibular overdentures were retained to the bars with either clips (group I, GI) or silicone resilient liners (group II, GII). The prosthetic and soft tissue complications of the maxillary dentures were recorded 6 months (T_6 m), 1 year (T1), 3 years (T3) and 5 years (T5) after overdenture insertion. Traced rotational tomograms were used for measurements of maxillary alveolar bone loss. The proportional value between bone areas and areas of reference not subject to resorption was expressed as a ratio (R). Change in R immediately before (T0) and after 5 years (T5) of overdenture insertion was calculated. Maxillary denture relining times and frequency of flabby anterior maxillary ridge occurred significantly more often in GI compared with GII. The change of R in anterior part of maxilla was significantly higher than change of R in posterior part in both groups. GI showed significant resorption of anterior residual ridge compared with GII. Relining times and frequencies of flabby ridge were significantly correlated with change in R. Within the limitations of this study, resilient liner attachments for bar‐implant‐retained mandibular overdentures are associated with decreased resorption and flabbiness of maxillary anterior residual ridge and fewer maxillary denture relining times when compared with clip attachments.     

Provisional implants for anchoring removable interim prostheses in edentulous jaws: a clinical study

PURPOSE: The behavior of provisional implants in edentulous maxillae/mandibles used for anchoring removable interim overdentures was followed for the time of the intended healing of the definitive implants. MATERIALS AND METHODS: Twenty-eight edentulous arches (19 maxillae, 9 mandibles) were provided with 77 provisional implants (2 to 4 in maxillae; 2 or 3 in mandibles) for anchoring removable interim prostheses (overdentures). The provisional implants were to be maintained until final restoration (6 to 9 months in the maxilla and 3 months in the mandible). The loss rate of provisional implants and handling and behavior of the anchored overdenture were monitored until the definitive prosthetic restoration was placed. RESULTS: Twenty-three (29.8%) of the 77 provisional implants were lost prematurely. The loss rate of maxillary provisional implants (21/58; 36.2%) was significantly higher than that of mandibular implants (2/19; 10.5%) (P < .01). Determination of terminal stability (by means of the Periotest) of the provisional implants showed higher stability in the mandible (+3.8 +/- 2.3) than in the maxilla (+8.6 +/- 3.9) (P < .05). In obvious contrast to mandibular interim overdentures, handling of maxillary interim overdentures was found to improve significantly during the follow-up period (P < .01). DISCUSSION AND CONCLUSION: With both the low loss rate in the mandible and the higher loss rate seen in the maxilla, placement of provisional implants fulfills the requirements for initiating immediate prosthetic rehabilitation. The removable interim overdenture can be adequately stabilized and provides for added patient comfort and satisfaction as compared to a conventional complete denture. An important aspect of the continued use of provisional implants concerns the expectations placed in these implants by both clinician and patient, which are quite different than those for definitive implants.     

种植体数目与分布对下颌种植覆盖义齿骨组织应力变化的影响

目的：建立下颌种植覆盖义齿三维有限元模型,研究咬合力作用下种植体数目与位置分布对牙槽骨组织应力分布的影响因素。方法：临床采集患者下颌骨及其原有义齿CT数据,使用逆向工程软件建立种植体数目与位置不同的下颌种植覆盖义齿实体模型。通过Abaqus有限元软件分析咬合力作用下种植体数目与位置分布对种植体周围以及下颌后端牙槽骨应力变化的影响。结果：在咬合力作用下,下颌骨Mises应力主要分布在种植体周围骨组织,种植体远中颈部呈现应力集中,下颌后端区域应力较小且分布均匀。随着种植体数目的增加,后端种植体周围骨应力上升,远端牙槽骨应力降低。当牙弓前、后端种植体距离增加时,种植体周围骨应力增大,远端牙槽骨应力降低。结论：采用2植体支持的下颌种植覆盖义齿种植体周围骨吸收风险较小,但远端牙槽嵴骨吸收风险增大。4植体义齿所承受的咬合力主要由植体承担,修复时应注意前后植体的距离和咬合力在义齿上的合理分布。     

Assessment of states of dentures and interest in implant-retained prosthetic treatment in 55-year-old edentulous Finns

Abstract – One hundred and fifty 55-year-old edentulous subjects (104 women and 46 men) were interviewed. Materials, conditions, functional stabilities, and occlusions of complete dentures, and resorption of alveolar crests were recorded and assessed. The dentures were in good condition in 52% of subjects. Occlusion was correct in 45% of cases. Every fifth mandibular denture exhibited good functional stability. The mean age of dentures in good condition and functionally stable was statistically significantly lower than the mean age of dentures poor in these respects. Severe alveolar resorption contributed to poor functional stability of dentures ( P = 0.0068 (maxilla), P = 0.0023 (mandible)) and to incorrect occlusion ( P =0.0177). Good agreement was noted between objective and subjective opinions of denture function ( p = 0.01 (maxillary denture), P = 0.01 (mandibular denture)). Although oral rehabilitation with endosseous implants is common and, objectively, needs for such treatment existed, only 22 subjects (15%) who had recently had their dentures renewed and were experiencing problems with functional stability were interested in implant-retained overdentures.     

Comparing the efficacy of mandibular implant-retained overdentures and conventional dentures among middle-aged edentulous patients: satisfaction and functional assessment

PURPOSE: The aim of this randomized clinical trial was to compare the relative efficacy of mandibular overdentures retained by only two implants and a bar attachment with conventional dentures. MATERIALS AND METHODS: Edentulous adults, aged 35 to 65 years, were randomly assigned to two groups that received either a mandibular conventional denture (n = 48) or an overdenture supported by two endosseous implants with a connecting bar (n = 54). All subjects rated their general satisfaction and other features of their original dentures and their new prostheses (comfort, stability, ability to chew, speech, esthetics, and cleaning ability) on 100-mm visual analogue scales prior to treatment and 2 months postdelivery. Oral health-related quality of life was also evaluated pre- and posttreatment. RESULTS: Multiple regression analysis revealed that the mean general satisfaction was significantly higher in the overdenture group than in the conventional denture group (P = .0001). Age, gender, marital status, and income were not significantly associated with ratings of general satisfaction. Furthermore, the implant group gave significantly higher ratings on three additional measures of the prostheses (comfort, stability, and ease of chewing; P < .05). CONCLUSION: A mandibular two-implant overdenture opposed by a maxillary conventional denture is a more satisfactory treatment than conventional dentures for edentulous middle-aged adults.     

Two-implant mandibular overdentures: simple to fabricate and easy to wear

Success rates for titanium dental implants in the anterior mandible are very high. Because of these success rates, as well as lower costs, it is common to treat edentulous patients with just 2 implants and ball anchors for retention of the overdenture, instead of 4 implants and a bar. In this paper the fabrication of 2-implant overdentures is described. In a controlled clinical trial (to be reported elsewhere), 30 subjects received a 2-implant overdenture for the mandible and a conventional prosthesis for the maxilla. The 30 control patients received conventional complete dentures for both jaws. The stability of the overdentures was excellent, and the lingual dimensions of the denture could be reduced to the level of the mylohyoid line to provide more space for the tongue. In patients with tense labial musculature or a limited amount of attached gingiva, it was important to elevate the shoulder of the implant and ball abutment above the gingival level to avoid peri-implant problems. Significantly fewer visits for adjustment related to post-placement pressure spots were required for mandibular overdentures than for conventional mandibular prostheses.     

Patient satisfaction with different types of implant-retained overdentures in the edentate mandible

The purpose of this study was to determine patient satisfaction with implant supported mandibular overdentures using magnet, bar-clip and ball-socket attachments, and to assess the relation between maximum bite force and patient satisfaction. In a crossover clinical trial, 18 edentulous patients with lower denture complaints received 2 mandibular implants and new lower and upper dentures. The lower denture initially came without any kind of attachment system, but was fitted with one of the attachment types after 3 months. The attachments were changed 3 months thereafter, in random order. A questionnaire concerning denture complaints was given at baseline (with the old denture), after 3 months of functioning with the new denture without attachments and after 3 months of functioning with each of the attachments (within-subject comparison). In addition, at the end of the experiment patients were asked to express their overall satisfaction with their dentures on a visual analogue scale (VAS). Data regarding maximum bite force were obtained from a previous study with the same population. Mandibular implant supported overdenture treatment reduced various denture complaints. The VAS score reflected patients' preference more accurately than scale-scores. Patients strongly preferred bar-clip (10 subjects) and ball-socket attachments (7 subjects) over magnet attachments (1 subject). Patients' preference could not be predicted on the basis of baseline observations. Maximum bite force was not correlated to scale- or VAS scores.     

Long-term effects on chewing with mandibular fixed prostheses on osseointegrated implants

Twenty-seven edentulous patients with denture adaptation problems were first given optimal conventional complete dentures and then a fixed prosthesis on osseointegrated dental implants in the lower jaw (and a complete maxillary denture). Masticatory function was evaluated by means of a questionnaire, a comminution test for chewing efficiency, and bite force measurements on four occasions: with the original (I) and optimal complete dentures (II) and 2 months (III) and 3 years (IV) after insertion of the fixed mandibular prosthesis on implants. No significant improvement of masticatory function was found after conventional denture treatment. After insertion of the fixed mandibular implant bridge, a marked improvement of the patients' assessment of their chewing ability and of the results of the chewing efficiency test and the bite force measurements was recorded. The test results were further improved after the 3-year observation period, which indicates that adaptation to the new prosthetic situation is a gradual process.     

Changes in the edentulous maxilla in persons wearing implant-retained mandibular overdentures

STATEMENT OF PROBLEM: It has been suggested that risk for severe resorption in the anterior maxilla is increased in persons wearing mandibular implant-retained overdentures. However, little information is available about the changes in the edentulous maxilla after mandibular implant treatment. PURPOSE: This study determined the possible changes in the width of the maxillary residual ridge 6 years after receiving mandibular implant-supported or implant-mucosa-supported overdentures and evaluated the association between the anatomic changes and subjective complaints with maxillary complete dentures. METHODS AND MATERIAL: The subjects for this study (n = 55), enrolled among the participants of a prospective clinical trial, were randomly assigned into 3 groups treated with: (a) implant-supported overdentures on a transmandibular implant system (n = 21); (b) implant-mucosa-supported overdentures on 2 IMZ implants (n = 20); or (c) conventional complete dentures (n = 14). A lingual contact occlusion concept with anterior open bite was used for tooth arrangement in all subjects. Diagnostic casts were made at baseline, and again at the 6-year follow-up. Most prominent points perpendicular to the crest of residual ridge were located in the incisor, canine, and premolar regions, after which the width of the ridge was recorded at these points with a Boley gage. Subjects' opinions on their dentures were evaluated with a questionnaire. RESULTS: Significant reduction in the width of the ridge was found in all measurement areas (mean difference = 0.4 to 0.6 mm; P <.0001). However, changes were small and not associated with the type of prosthetic restoration in the mandible. In subjects with implant-mucosa-supported overdentures, complaint of loose maxillary denture correlated with the decrement of residual ridge width. CONCLUSION: The width of residual ridge decreases with time, despite the type of mandibular prosthetic restoration.